Scaling Stress Seeds

  Stress seeds provide an interesting example of the processes considered above by which scalar, vector, and tensor metric perturbations are generated and affect the temperature and polarization of the CMB. They are also the means by which cosmological defect models form structure in the universe. As part of the class of isocurvature models, all metric fluctuations, including the (scalar) curvature perturbation are absent in the initial conditions. To explore the basic properties of these processes, we employ simple examples of stress seeds under the restrictions they are causal and scale with the horizon length. Realistic defect models may be constructed by superimposing such simple sources in principle.

We begin by discussing the form of the stress seeds themselves (§VA) and then trace the processes by which they form metric perturbations (§VB) and hence CMB anisotropies (§VC).